bug #1595348 by Ron pointed out this flaw and fix

lib/config-win32.h

@@ -290,11 +290,9 @@
 /* Define as the return type of signal handlers (int or void).  */
 /* #define RETSIGTYPE void */
 
-/* Define to `unsigned' if size_t is not an available 'typedefed' type */
-/* #define size_t unsigned */
-
-/* Define to 'int' if ssize_t is not an available 'typedefed' type */
 #if (defined(__WATCOMC__) && (__WATCOMC__ >= 1240)) || defined(__POCC__)
+#elif defined(_WIN64)
+#define ssize_t __int64
 #else
 #define ssize_t int
 #endif